The Tianjin Metro or Tianjin Rail Transit is the rapid transit system in the city of Tianjin, which was the second city in mainland China after Beijing to operate a subway system. First opened in 1984, the system currently has 10 operating lines and 217 stations spanning 301 km (187.0 mi).

Tianjin is a municipality and metropolis in Northern China on the shore of the Bohai Sea. As such, it is not part of a province of China. It is one of the nine national central cities in Mainland China, with a total population of 13,866,009 inhabitants at the time of the 2020 Chinese census. Its metropolitan area, which is made up of 12 central districts, was home to 11,165,706 inhabitants and is also the world's 29th-largest agglomeration and 11th-most populous city proper.